A wide range of medical treatments are known that utilize “endoluminal prostheses.” As used herein, endoluminal prostheses are intended to mean medical devices that are adapted for temporary or permanent implantation within a body lumen, including both naturally occurring and artificially made lumens. Examples of lumens in which endoluminal prostheses may be implanted include, without limitation: arteries, such as those located within the coronary, mesentery, peripheral, or cerebral vasculature; veins; gastrointestinal tract; biliary tract; urethra; trachea; hepatic shunts; and fallopian tubes.
Various types of endoluminal prostheses are also known, each providing a component for modifying the mechanics of the targeted luminal wall. For example, stent prostheses are known for implantation within body lumens for providing artificial radial support to the wall tissue, which forms the various lumens within the body, and often more specifically within the blood vessels of the body.
To provide radial support to a blood vessel, such as one that has been widened by percutaneous transluminal coronary angioplasty, commonly referred to as “angioplasty,” “PTA” or “PTCA”, a stent is implanted in conjunction with the procedure. Under this procedure, the stent may be collapsed to an insertion diameter and inserted into a body lumen at a site remote from the diseased vessel. The stent may then be delivered to the desired treatment site within the affected lumen and deployed, by self-expansion or mechanical dilation, to its desired diameter for treatment.
Although systems and techniques exist that work well in many cases, no technique is applicable to every case. For example, special methods exist for dilating lesions that occur in branched or bifurcated vessels. A bifurcation is an area of the vasculature where a main vessel is bifurcated into two or more branch vessels. It is not uncommon for stenotic lesions to form at such bifurcations. The stenotic lesions can affect only one of the vessels, i.e., either of the branch vessels or the main vessel, two of the vessels, or all three vessels.
Implanting a stent at a bifurcation in a body lumen poses various challenges for the effective treatment of stenoses in the lumen. For example, dilating a vessel at a bifurcation may cause narrowing of an adjacent branch of the vessel. In response to such a challenge, attempts to simultaneously dilate both branches of the bifurcated vessel have been pursued. These attempts include deploying more than one balloon, more than one prosthesis, a bifurcated prosthesis, or some combination of the foregoing.
However, stent implantation at a bifurcation is particularly prone to undesirable reactions such as restenosis, inflammation, infection, thrombosis, and proliferation of cell growth that occludes the passageway because a bulk of material (such as, for example, overlapping or abutting stent struts) often occurs at some point along the bifurcation and acts as an initiation site for thrombus and/or restenosis. For example, when abutting stents are deployed in each of the branch or leg vessels, often abutting stent material extends across the middle of the main vessel thus interrupting the blood flow path. To assist in preventing these conditions, stents have been used with coatings to deliver drugs or other therapeutic agents at the site of the stent. However, it would be desirable to provide a bifurcation stent system having a design or structure that allows for less turbulent blood flow therethrough and thus minimizes undesirable reactions such as those listed above. Accordingly, there exists a need in the art to eliminate or decrease the amount of stent metal that is left in the blood flow path of the main vessel of the bifurcation.